When 18.0 mL of a 1.80×10-4 M ammonium iodide solution is combined with 18.0mL of a 7.33×10-4 M silver fluoride solution does a precipitate form?

Question

When 18.0 mL of a 1.80×10^-4 M ammonium iodide solution is combined with 18.0mL of a 7.33×10^-4 M silver fluoride solution does a precipitate form?  _____ (yes or no)

For these conditions the Reaction Quotient, Q, is equal to ____.

Answer 1

To determine if a precipitate forms, you compare Q (the reaction quotient) to the Ksp (the solubility product) which is a value you can look up.

Let’s calculate Q:

NH₄I(aq) + AgF(aq) ==> NH₄F(aq) + AgI(s)

[Ag⁺] = 18 ml x 7.33x10^-4 M/36 ml = 3.67x10^-4 M

[I^-] = 18 ml x 1.8x10^-4 M/36 ml = 9x10^-5 M

Q = [Ag⁺][I^-] = (3.67x10^-4)(9x10^-5) = 3.3x10^-8

Compare this value to the Ksp for AgI (8x10^-17) and since it is greater than tge Ksp a precipitate WILL form.